Nitrogen-vacancy (N-
V) centers in diamond are widely used in quantum information science, but existing methods to fabricate N-
V centers rely on damaging the diamond lattice, and usually lead to poor optical coherence. The authors propose a nondestructive method, where high-purity diamonds are annealed under high pressure and high temperature, to generate N-
V centers with excellent optical, spin, and charge properties. These results provide new insights into the diffusion dynamics of defects under extreme conditions, and indicate that even the ultrapure diamond contains enough nitrogen and vacancies to form N-
V centers.
We report the optical observation of lead-vacancy (PbV) centers in diamond fabricated by Pb ion implantation and subsequent high-temperature annealing (2100 °C) under high pressure (7.7 GPa). Their optical properties were characterized by photoluminescence at varying temperatures down to 5.7 K. We observed intense emission peaks at 550 and 554 nm, with a large splitting of approximately 3900 GHz. The two lines are thought to correspond to the zero phonon line (ZPL) of PbV centers with split ground and excited states. A cubic trend of the ZPL width was observed while varying the temperature. We performed polarization measurements of the two lines in a single PbV center, showing nearly orthogonal dipole polarizations. These optical measurements strongly indicate that the PbV center possesses D 3 d symmetry in the diamond lattice. The observed large ground state splitting significantly suppresses the phonon-mediated transition, which causes decoherence of the electron spin state of the group IV color centers in diamond, leading to the expectation of a long spin coherence time at a temperature ∼9 K.